Abstract
Wetland birds are among the most sensitive indicators of freshwater ecosystem condition, yet the fine-scale habitat
features determining their space use, guild-specific microhabitat selection, and foraging site fidelity are incompletely
characterised across the gradient from natural to human-modified wetlands. This study quantified habitat utilisation
patterns for twelve wetland bird species across six functional guilds (piscivores, herbivores, probers, surface-feeders,
aerial insectivores, and omnivores) at 18 wetland sites spanning natural fen, managed reedbed, restored polder, and
urban stormwater pond types in Switzerland, the Netherlands, and Sweden (n = 9,284 individual detections, 2022-2023).
GPS-GSM telemetry (n = 64 tagged individuals across four species) and point-count surveys were combined with
vegetation structure mapping and water chemistry profiling. Resource Selection Functions (RSF) identified water depth
(0.2-0.8 m), emergent vegetation cover (40-70%), and open water patch size (> 0.3 ha) as the three most consistent
positive habitat predictors across guilds (all beta > 0.42, p < 0.001). Piscivore species (Ardea cinerea, Alcedo atthis)
showed the strongest selection for clear water (Secchi depth > 0.6 m; RSF beta = 0.81 and 0.74 respectively). Restored
polder wetlands supported 68.4% of the species richness found at natural fen sites and demonstrated equivalent core
habitat quality for three of four telemetered species based on kernel density utilisation distribution (KDE95) overlap
analysis. Urban stormwater ponds supported the lowest species richness (mean 4.2 +- 1.1 species) but maintained
viable foraging habitat for Anas platyrhynchos and Fulica atra. These results provide guild-specific habitat management
targets for restored and managed wetlands under the EU Birds Directive and Ramsar Convention obligations.